Bearing torque test instrument



Aug. 24, 1965 T. P. BARNARD 3,201,981

BEARING TORQUE TEST INSTRUMENT Original Filed Feb. 25, 1957 3 Sheets-Sheet 1 a INVENTOR THEODORE P BARNARD FW,W W, BY We M am ATTORNEY Aug. 24, 1965 T. P. BARNARD 3,201,981

BEARING TORQUE TEST INSTRUMENT Original Filed Feb. 25, 1957 3 Sheets-Sheet 2 FIG. 2

QUE INVENTOR GENERATOR THEODORE P BARNARD 1 BY W M,

ATTORNEY Aug. 24, 1965 1-. P. BARNARD 3,201,981

BEARING TORQUE TEST INSTRUMENT Original Filed Feb. 25, 1957 3 Sheets-Sheet 3 FIG. 6

OSCILLATOR PHASE 82 SHIFTER OUTPUT l AMPLIFIER 85 EXCITATION O AMPLlFlER s3 GAIN 0 GAIN 86 sENsE DETECTOR REFERENCE AMPLIFIER O BALANCE 1 0 TORQUE GENERATOR o 1 VARIABLE F FILTER TORQUE GENERATOR /9| 1 0c. SUPPLY cuRRENT CONTROL Q S B R D E R INVENTOR ATTORNEY United States Patent Office 3,201,981 Patented Aug. 24, 1965 Original application Feb. 25, 1957, Ser. No. 642,090, now

Patent No. 3,027,749, dated Apr. 3, 1962. 'Divided and this application Mar. 6, 1962, Ser. No. 184,625

7 Claims. (Cl. 73- 133) This application is a division of the pending application, Serial No. 642,090, filed February 25, 1957, now Patent No. 3,027,749 and assigned to the same assignee as the present application. The claims herein are directed to the apparatus shown in FIGS. 16 of the pending application.

- The present invention relates to instruments for testing bearings of the type having inner and outer race members and rolling elements therebetween, and in particular to an instrument adapted to test such a bearing by providing an accurate measurement of the running torque transmitted from one race member to the other race member by imperfections in the coacting surfaces of the race members and rolling elements.

Specific bearing imperfections measurable by means ofthis running torque test include out-of-roundness, eccentricity, Waviness, and finish of the coacting race member and rollingelernent surfaces. These imperfections are characterized by the production of pulses of transmitted torque. The frequencies of recurrence of the transmitted torque pulses extend through a range of up to approximately 20 cycles per second in accordance with the imperfections causing the pulses. Pulses due to out-ofroundness and eccentricity of the coacting surfaces are characterized by frequencies at the low end of this frequency range; pulses due to waviness are characterized by frequencies in the middle of the frequency range; and pulses due to finish are characterized by frequencies at the high end of the frequency range.

It is one of the objects of the present invention to provide a bearing test instrument capable of accurately measuring pulses of transmitted torque regardless of the frequency of pulse repetition.

To this end the instrument of this invention is adapted to apply a torque to one of the race members of a test hearing. The torque is transmitted from this driving race member through the rolling elements within the bearing to the other, or driven, race member causing the driven race member to rotate. Measurement of the transmitted torque to be effected by means of a rotation-restraining system, analogous to a spring, which prevents further rotation of the driven race member at some equilibrium position displaced from its normal or null position. The torque required to maintain the driven race member at this equilibrium position is then indicative of the average transmitted torque or constant torque level produced by rolling friction and lubricant drag in the bearing. The surface imperfections producing the pulses of transmitted torque cause the driven race member to fluctuate about this equilibrium position in response to the action of the rotation-restraining system. A measurement of the instantaneous torque applied by the rotation-restraining system therefore provides an accurate indication of the magnitude of the transient pulses of transmitted torque and the average torque level about which they fluctuate.

In this instrument the range and linearity of frequency response to pulses of transmitted torque is proportional to the moment of inertia I, and the spring constant k, of the rotation-restraining system in accordance with the equation T =21r\/l k, where T is equal to the period of the system. Thus the lower the moment of inertia, and the higher the spring constant, the greater the linear frequency tive relationship with the rotor.

range of the instrument. A large spring constant results in the loss of instrument sensitivity, however, and is therefore undesirable for many applications.

The present invention is featured by a rotation-restraining system the moving elements of which have an exceptionally low moment of inertia, thus permitting the spring constant of the system to be maintained low enough for optimum instrument sensitivity while providing a linear frequency response over the desired range of torque pulse repetition frequency.

To this end the bearing instrument is provided with a shaft adapted to mate with the inner race member of a test bearing. The shaft is .rotatably mounted in a housing adapted to apply a torque to the outer, or driving, race member of the test bearing. The driving torque is thus transmitted through the bearing rolling elements to the inner, or driven, race member and thence to the shaft.

The rotation-restraining system includes an electrical signal generator. The rotor of this generator is mounted upon the shaft in coaxial symmetry therewith. The stator of the generator is mounted on the housing in opera- In this way the radius of gyration of the rotor about its centroidal axis is maintained as low as possible, thus providing a low moment of inertia.

The invention further provides a torsion element attached to the shaft and arranged in coaxial symmetry therewith. The torsion element is adapted to apply a restoring torque to the shaft in proportion to its angular displacement. The shaft is thus restrained at some equilibrium position indicative of the magnitude of the torque transmitted to the driven race member. To measure this torque the signal generator is adapted to produce an output voltage signal proportional to the angular displacement of its rotor.

The preferred embodiment employs an electrical torque generator to provide the required restoring torque. The rotor of the torque generator is mounted on the instrument shaft in coaxial symmetry therewith to maintain a low shaft moment of inertia. The stator of the torque generator is mounted on the housing inoperative relationship with its rotor.

Electrical connecting means are then provided for applying the output signal from the signal generator to the torque generator. The torque generator is adapted to produce a restoring torque on its rotor proportional to this output signal. In this way the shaft is again restrained at an equilibrium position indicative of the magnitude of the torque transmitted to the driven race member.

A particular advantage of the above-described torsion element embodiment is that it permits adjustment of the spring constant k through a range of values. This enables the choice of an optimum value of k for the bearing being tested. Such adjustment is preferably effected by varying the value of electrical excitation applied to the stator of either the torque or signal generator.

The linear and wide frequency response afforded by the instrument of this invention permits the observation of bearing characteristics heretofore unobtainable with the instruments of the prior art. For example, the composite torque transmitted to the driven race member of the test bearing may be analyzed in terms of frequency by suitable filtering of the output signal of the instrument. This permits observation of the torque contribution due to the various bearing imperfections.

In a preferred embodiment of the electrical signal generator, and the torque generator as well, the stator comprises four symmetrically-disposed poles concentrically arranged about the associated rotor element. The rotor element is of magnetic material and is not permanently magnetiaeitnor does it..carry..any windings... It has :two 3 diametrically-opposed circular end portions, each substantially spanning the distance between the centers of t a a en P01682111? p fac b i lfor dtop v n: a ur tel uni orm i ap wit rel ot h nd of the rotor. Suitable windings-are then provided about the stator poles: of; each generatorin accordance. with the functitm. h l e at r t e Windi p te n b such that each rotor has a normal or neutral position with the edges of its circular end portions at the centers of the P l faces e$$Q sd W t u a eni d pa e ns fqr' q liih s na endto n e e tq slare d scribed in Patent No. 2,488,734, issued to R KQMueller. on Nsr mber. 2; 1 ,9 and ent e DY amq m former. 2 Th s a pa a lyui o tant dy n a in: ear n t que, measurement T e. na q ne ipn is, h sen i veaen y prefer e i n i it r .i ibsd ri n iirr d 23which may be'quite small in diameter.

' an axial thrust load isapplied downwardly upon the bear-.

ing during the torque, test in accordancewith' conventional testing standards; These standards may designate a number'of xynu'e'sbr thrustjload Means for'the'reception upon shaft 33 of' calibrated weights, such as 42, is therefore'provided in, the form of a shoulder 24. It will be to v angular displacement andnotradial displacement,

Off-center translation does not therefore affect the accuracy of the system, thus eliminating the necessity for maintaining very close'and,expensive'tolerances. j 1 jv The invention can best he understood ;by referring; to the following drawings in which: a 1 Y FIG. 1 is an elevation view partly in cross-sectionjof one embodiment'ofthebearing torque test instrument of this invention;

FIG. 2 is an enlarged cross-sectional view of the test bearing support employed in 1 16. 1; 3

FIG. 3 is a view of the servoloop system FIG. 1 taken along line -33;

FIG. 4 is ascl ematic diagram of a signal generator winding pattern which may be employed in the servolo op emri edi system of FIG. l; V t l J 1 p l I s I .5. e fis dia r m o a or u e rator. winding pattern .which'may-be employed in the servoloop system of E1641; and 1 FIG. 6 is a block diagram ponentsemployed with-thesignalgand torque generators of servoloop ,electricalicorn-i' noted that Weight 42. is oriented in coaxial relationship" with. shaft-33 so that its weight. is distributed equally about the axis of the shaft, hereby minimizingthemoment of in-.

ertiaj of'the rotating portion of the instrument. J Ejecting lever 43; pivoted onto spring 44, is provided to lift (the shaft 33 so that the units m'ounted' at the upper end of the:shaft'may;be raised'clearof rotor adapter 32and easily remqved.

-Thus'we, see- 'tliat. in the present invention a torque is appliedto, theouter race 31 of .test bearing 30 by means of rotor-15 through rotor adapter 32; 'As has been mentionedhe'retofore imperfections in the coacting surfaces 1 of the bearingEroller;elements 43. and the inner and outer race members. 37 and 31 will transmit a portion of the torque applied to the outer; or driving, race member 31 to the inner, or driven, race member 37. By means of shaft adapter 36 this transmitted torqueis in turn'applied' from inner race member 37m shaft 33. Thus a meas- V urementof. the torque applied to shaft 33 is indicative ofv this transmitted torque and therefore of imperfections in the test bearing.

The'torque transmitted to shaft 33 is measured by' means. of a rotation-restraining system comprising. a servoloop.having asignal generator indicated generally v ReferringtoIFIG. l'the torqne test instrument. corn;-

p rises a cylindrical housing 10 perpendicularly supported upon a base'll by means; of screws 12. Leveling screws 13 and a level bubble 14 are. provided to verticallyorient housing 10. A rotor 15 is supported on'housing 1 0iby means of bearings l'6 and lockring s l7 and 18. Motor 21, pulley 20; and belt 19 a re provided to drive the rotor 21 is supported on base ll vby means of 15.; The motor bracket 22.

QTOrquefrom rotor 15 is appliedto the shame at, and a torque generator indicated generally at 51. FIG, 3 .is a view; of the torque generator taken along line 3- 3 of FIG-.1. Since the; torque generator and the sig- 7 nalgenerat or' are identicalin physical construction the a view ofthe torque generatorraiforded by FIG. 3 will be adequate for a description of both; I I

"Each ge nerator hasa rotor elementSZ Tin'the signal generatorandf53 in" the: torque generator. These rotors of the test bearing 30 byrnea'ns of adapter 32. 1 As is best j seen in FIG. 2 the. outer race 31of the bea ring isqseated upon shoulder 40 of adapter- 32/ The vertical inside" diameter of shoulder 40. is. accuratelymachined to snugly embrace the outer diameter; of ojuterracemember 31.. The bearings to be tested may vary in size of outerrace outer diameter. In that event a variety ofadapters hav- 1 ing. differently dimensioned insi 40 may beprovided. I i I l 1 I Shaft 33 is positioned in axial coin cidence with: hous-j ing 1.0 ;by means ofa jewel assembly -34 and jewel-lock ring 35, at one end; an d shaft adapter 36 at theotherf end.

Adapter 36 is provided to adjust the outside diameter of extension-23 of shaft 33 to the inside diameter of the testg bearing inner race37. In the event the test bearings vary in size,v a varietyl of shaft adapters may be provided to adjust the shaft diameterto the inner race inner diameters of the various bearings to be tested. i

The outside diameter 41; of-shaft' adapter 36 is accu rately machined to mate snugly with the inside diameter of innerrace member 37. Screw member 38 is threaded within adapter 36 to apply pressure against balls 39 which act like the 'jaws of a chuck to lock shaft 33 within adapter de diameters of shoulder smaller diameter portions 54 and '55f'of shaft 33. The rotors are clamped against these shoulders by means of are mounted upon shaft 133 in coaxial symmetry there with. .;The-shaft is employed'to transfer the transmitted torquew frorntheIdriven race member to the generator The; rotors are mounted on the shaft upon the I rotors; shoulders. providedby the large diameter portion 56 and bolts'57. I I v I Eachrgeneratorals'o includes a stator 58 inthe signal generator and 59 in the torque generator. Each stator is attached to the honsinglfl in operative relationship with its associated rotor element.

,rnoinent'of inertia of the rotating parts. that such coaxial orientation of shaftaccessories is main- Thecoaxial-orientation of rotors 52and 53 with respect to shaft 33 is again intended for equal weight distribution about the shaft axis and minimization of the tained throughout the instrument. A- variety of signal and torque generators may beemployed to perform the a torque measuring function in the'fprese'nt invention. Applicable-signal and torque generators are described'in 36, This chuck-like assembly is employed to avoid-the threading and consequent weakening of shaft extension chapter 10, entitled Rotary Inductors, of Blackburns Components Handbook, vol. 17,of the Massachusetts T Institute of Technology Radiation Laboratory. Series.

Measurement of the transmitted torque applied to the: shaft 33 is eifected'by the signal end torque generatorsin the following manner.' The signal generator and lfquergefierator'i both; have :a; null or: .neutral position i when not disturbed by the applicationof torque to the It Will be noted shaft. The signal generator 51 is adapted to produce an output signal in proportion to the angular displacement of its rotor 52. Thus when a torque is transmitted to the shaft 33 the rotation of the shaft, and consequently of the rotor 52, upsets the null balance of the signal generator and produces a signal proportional to the degree of angular displacement.

Suitable means are provided to apply this output signal to the torque generator 51. The torque generator is adapted to apply a restoring torque on its rotor 53 in proportion to the output signal from the signal generator.

I Thus the shaft 33, and consequently rotor 52, will be angularly displaced from the null position until the signal output to the torque generator has produced a restoring torque on rotor 53 equal and opposite to the transmitted torque. The equilibrium position of the shaft, or the output signal from the signal generator, is therefore indicative of the restoring torque which in turn is equal to the transmitted torque. Measurement of the output signal is, of course, the simplest of the possible alternatives of transmitted torque indication. Such measurement also permits the employment of a recording device for making a permanent record of the transmitted torque characteristic of the particular bearing being tested.

With a servoloop system comprising signal and torque generators it is possible to vary the spring constant k of the rotation-restraining system by varying the excitation of either the torque or signal generator employed. This feature is particularly advantageous since the sensitivity of the instrument varies in inverse proportion to the spring constant k. Thus variation of the spring constant acts as an instrument sensitivity adjustment for a particular application or bearing.

A preferred construction of the signal and torque generators which has particular advantage in a bearing torque test application is illustrated in FIGS. 1 and 3. In this embodiment the rotor is made of magnetic material such as soft iron. The rotor is not permanently magnetized nor does it carry any windings. The stator is preferably constructed of laminations of magnetic material and has four symmetrically disposed, re-entrant poles 60, concentrically arranged about the rotor element associated therewith. The rotor has circular end portions 61, each of which substantially spans the distance between the centers of two adjacent poles. The pole faces are formed to provide accurately uniform air gaps with relation to the ends of the rotor.

FIGS. 4 and 5 represent stator windings for the signal generator and torque generator of the preferred servoloop embodiment. The stator windings illustrated in FIGS. 4 and 5 are by way of example only and are representative of a variety of windings that may be used to this purpose as more fully described in the hereinbefore noted Patent No. 2,488,734.

'Each pole of the stator 58 of signal generator is provided with a pair of windings and 71. The two windings are connected to separate inputs indicated as inputs A and B. In the convention employed in FIGS. 4 and 5 the direction of magnetomotive force is inward toward the rotor when induced by a coil marked i, and outward away from the rotor when induced by a coil marked 0. Thus the magnetomotive forces induced by the windings on the re-en-trant poles 72 and 73 respectively, reinforce one another, while the combined electromotive force on. pole 72 is opposite in direction to the combined electromotive force on pole 73. The windings on poles 74 and 75, respectively, are, however, coiled to induce canceling magnctomotive forces.

In operation of the signal generator 50 an alternating excitation voltage is applied to terminals A of primary winding 70. If the value of this excitation voltage is maintained constant the output signal at the terminals B of secondary winding 71 will be zero in value when the rotor is in its neutral or null position. This null position occurs when the edges of the rotors circular end portions 6 are located at the centers of the stator poles. If the rotor is moved the magnitude of the output signal will vary in proportion to the angular displacement of the rotor from neutral. The phase of this output signal differs by 180 depending upon the direction of angular displacement of the rotor from its neutral position.

The winding pattern of the torque generator 51 is identical to that of the signal generator 50. In this case, however, the excitation voltage is DC. and is applied to the terminals C of primary winding 76. The input to the terminals D of the secondary winding 77 is also a D.C. voltage. The torque tending to move the rotor from its neutral position is proportional to the magnitude of the voltage applied to the winding 77 when the excitation voltage applied to winding 76 is maintained constant. In addition the direction of this torque varies with the polarity of the voltage applied to winding 77.

The operation of the servoloop with this particular winding arrangement therefore requires electrical connecting means for converting the A.C. signal appearing at the output of coil 71 into a DC. voltage proportional thereto, and applying this voltage to coil 77 of the torque generator. The connecting means must also sense the phase of the A.C. output signal of the signal generator and produce a DC. voltage having the proper polarity to apply a restraining torque to rotor 53 opposite in direction to the direction of rotation of rotor 52 of the signal generator.

Such connecting means is illustrated in block diagram form in FIG. 6. Excitation voltage to the signal generator 80 is supplied from oscillator 81 which has both amplitude and frequency controls. The output of the oscillator is applied through a phase shifter 82 to excitation amplifier 83 having a gain control associated therewith. The gain of the excitation amplifier may be metered by means of A.C. meter 84-. This excitation voltage is applied to input terminals A of the primary winding of the signal generator 80.

The output of the signal generator is applied from ter minals B of its secondary winding to output amplifier 85 having a gain control associated therewith. The output of amplifier 35 is then coupled into a sense detector circuit 86. The function of the sense detector is to provide in combination with filter 87 a DC. output proportional to the A.C. output of amplifier 85, and to provide in combination with reference amplifier 88 a polarity shift of its DC. output in accordance with a phase shift of the input from amplifier 85. The construction of such sense detecting circuits is well known in the art.

This DC. output is then applied through DC. power amplifier 89 to the terminals D of the secondary winding of the torque generator 99. A torque generator D.C. supply, having a current control associated therewith, is provided to supply excitation voltage to the terminals C of the primary winding of the torque generator 99. Thus the torque generator is provided with a constant D.C. supply from the primary, and a DC. input to the secondary the magnitude and polarity of which causes a torque to be imparted to the rotor element of the torque generator which is opposite in direction and equal to the transmitted torque generating the output signal of the signal generator.

The current control adjustment provided in the torque generator D.C. supply 91 provides a simple means for varying the excitation of the torque generator and therefore the spring constant k of the system. Such spring constant variation may also be effected by the gain Control of the excitation amplifier 83 providing the alternating excitation voltage to the primary of the si nal generator 80.

Indication of transmitted torque is effected by a measurement of the output signal from the signal generator by means of voltage recorder 92. Variable filter 93 is provided for analysis of the imperfections causing the transmitted torque. Thus if the percentage of transmitted torque contributed by out-@of-roundness andeccentricity alone is required the variable filter may be adjusted to pass only the low frequency band of the total transmitted torque frequency range. Each torque contributing factor may be analyzed in a similar manner. u

The signal and torque generator embodiment illustrated and described possesses features which are particularly advantageous in a bearing torque test instrument. Firstly, the sensing ability of this servoloop system toangular displacement is approximately six seconds of arc,thus pro-- viding the extreme sensitivity required in bearing torque tests.

Secondly, and of great importance, this servoloop sys-- tem inherently has an inability to sense translation. This means that the torque tester mechanical drive units, even through'imperfectly made, cannot create erroneoussignals due to eccentricity, run-out, etc. Thus thetime consuming and expensive precision required to reduce these mechanical drive unit errors is eliminated by this feature.

It is interesting to note, however, that by tapping the windings at locations other than those employed for sens ing and restoring angular deflections the signal generator of this systemlends itself to the measurement of trans latory errors in the mechanical drive units of the instrument. Thus the signal generator may be employed to alignthe shaft and its accessories. 'In addition this provides a means for reading bearing geometry errorscompletely separated from torque.

In the course of the development of the present inven-' tion it was found that the servoloop system had a tendency to oscillate, thus partially obscuring torque measurement.

provide approximately 0.010 clearance therebetween The damping is effected by the fluid shearing required to move the extension relative to the cup and is proportional an indication representative of the said transmitted torque.

Z. A bearing torque test instrument in accordance with claim 1- in which the means for measuring the said torque generator restoring torque comprises means for measuring the said output signal from said signal generator.

3. A bearing torque test instrument for testing a bearing having inner andouter race members androlling elements disposed therebetween comprising a housing, ajshaft. rotatably mounted within said housing and adapted to mate with the inner race member of said testbearing, drivingmeans mounted on said housing and adapted to apply torque to the outer race member of said test bearing, "whereby a transmitted torque is applied to the said inner race member and shaft from the said outer race member through the said rolling elements therebetween, an electrical servoloop rotationrestraining system, comprising a signal generator and a 1 torque generator, each of said generators comprising a rotor element of magnetic material, a stator having an even numberof at least four symmetrically-disposed poles concentrically arranged about said rotor, said rotor having two diametrically-opposed circular end portions, each of said end portions substantially spanning the distance between the centers of at vleastfa pair of adjacent poles, the faces of said poles being formed to provide an accurately uniform air gap with relation to the endsof the said rotor, the said rotors being mounted on :said'shaft in coaxial symmetry therewith, each of the said stators being mounted onsaid housing in operative relationship withrthe rotor associated therewith, said signal generator stator being provided with a winding having a pattern which produces zero output signal at a null 1 position with the edges of the'said circular end portion to the velocity. This type of damping has beenjfound rotatably mounted within said housing and adapted to mate with the inner race member of said test bearing,

driving means mounted on said housing and adapted to apply torque to'the outerrace member of said'test hearing, whereby a transmitted torque is applied to the said inner race member and shaftfrom the said outer race 7 member through the said rolling elements therebetween, an electrical servolooprotation-restraining system. comprising a signal generator and a torque generator each having a rotor and a stator respectively, the said rotors being'mounted on said shaft in coaxial symmetry therewith, each of the said stators being mounted. on saidhousing inoperative, relationship with the rotorassociated therewith, said signal generator being adapted toproduce} an output signalin proportion to angulardisplacernent of its said rotor, electrical connecting means for, applying said output signal from said signal generator to the said 7O I torque generator, said torquegenerator being adapted to apply a restoring torque to its said'rotor in proportion to the said output signal applied thereto to restrain the said shaft at an equilibrium position indicative of themagni-- tude of said transmitted torque, and means for measuring the said torque generator restoring torque to, provide disposed at the center of the stator pole faces and which produces an output signal from said winding proportional in amplitude to angular displacement of said rotor from said null position, said torque generator stator being provided with a winding having a pattern adapted to maintain therotor of said stator in a null position with the edges of its said circular end portions substantially at the centers of a pair of pole faces of said stator and to apply a restoring torque-to said rotor in proportion to the signal applied to said Winding, electrical connecting means for applying said output signal from said signal generator winding to the said torque generator winding, whereby the restoring torque applied to the said torque generator rotor restrainsthe said shaft at anequilibrium position indicative of the magnitude of the said transmitted torque, and means for measuring the said torque generator'restoring torque to provide an indication representative of the said transmitted torque.

4. 'A hearing torque test instrument in accordance with claim 2 which includes means for varying the excitation voltage applied to the winding of at leastone of said'signal or torque generators;

5. A bearing torquextest instrument in accordance with claim 2 which includes means for damping the rotational motion of the said shaft, said means including a cup mounted on said housing and partially filled with a linear viscous damping, fluid and a cylindrical rotor cap mounted] in coaxial symmetry withpsaid shaft and adapted *to' project into the said damping fluid.

. 6. Abearing test instrument forcontinuously measuring the running torque of a test bearing having inner and outer racemembers and rolling elements disposed therebetween comprising a base housing, 7

- rotor means rotatably-mounted on said housing and f defining a central aperture adapted'to'embrance and supportlthe outer race of said bearing, V a shaft adapted to mate with the inner race member of said. test :bearing and to suspend therefrom at its 'upper' end to apply, an axial load on said test bearm I 1 guide bearing means mounted in said base housing 1 :adapted to radially support the lower, end of said shaft for rotation while permitting vertical movement thereof,

means mounted on said housing for driving said rotor at a predetermined substantially constant speed, whereby said outer race is rotated and a transmitted torque is applied to the said inner race memher and said shaft from the outer race member through the rolling elements therebetween,

' a torsion element attached to said shaft and arranged in coaxial symmetry therewith, said element being adapted to apply substantially only a rotational restoring torque to the said shaft in response to its angular displacement to restrain the shaft at an equilibrium position indicative of the magnitude of said transmitted torque,

an electrical signal generator having a rotor mounted on said shaft in coaxial symmetry therewith and a stator mounted on said housing in operative relationship with said rotor,

said signal generator being adapted to produce an output signal proportional in amplitude to the angular displacement of the shaft and rotor and being substantially insensitive to shaft displacement in translation,

and means for measuring the said output signal from said signal generator, said output signal being representative of the magnitude of said transmitted torque.

7. A bearing test instrument for continuously measuring means mounted on said housing for driving said rotor at a predetermined substantially constant speed, whereby said outer race is rotated and a transmitted torque is applied to the said inner race member and said shaft from the outer race member through the rolling elements therebetween,

an electrical servo-loop rotation-restraining system comprising a signal generator and a torque generator each having a rotor and a stator respectively, the said rotors being mounted on said shaft intermediate said guide bearing and said test bearing in coaxial symmetry therewith, each of said stators being mounted on said housing in operative relationship with the rotor associated therewith, said signal generator being adapted to produce an output signal in proportion to angular displacement of its said rotor,

electrical connecting means for applying said output signal from said signal generator to the said torque generator, said torque generator being adapted to apply a restoring torque to its said rotor in proportion to the said output signal applied thereto to restrain the said shaft at an equilibrium position indicative of the magnitude of said transmitted torque,

and means for measuring the output signal from said signal generator to indicate the magnitude of said transmitted torque.

References Cited by the Examiner the running torque of a test bearing having inner U IITED STATES PATENTS and outer race members and rolling elements disposed L therebetween comprising a base housing, 2009997 8/35 Germond 73.47 tor mean rotatably mounted on said housing and 2468648 4/49 Abbott et 73 67 defining a central aperture adapted to embrace and 2488734 11/49 Mueller 318 24X support the outer race of said bearing, 2722824 11/55 Jensen et a1 73 9 a shaft adapted to mate with the inner race member gig? et E of said test bearing and to suspend t e e at lts 2,877,949 3/59 Briggs X upper end to apply an axial load on said test bearing, a guide bearing means mounted in said base housing adapted to radially support the lower end of said RICHARD QUEISSER Prlmary Exammer' shaft for rotation while permitting vertical movement 4 ROBERT L. EVANS, Examiner.

thereof, 

1. A BEARING TORQUE TEST INSTRUMENT FOR TESTING A BEARING HAVING INNER AND OUTER RACE MEMBERS AND ROLLING ELEMENTS DISPOSED THEREBETWEEN COMPRISING A HOUSING, A SHAFT ROTATABLY MOUNTED WITHIN SAID HOUS ING AND ADAPTED TO MATE WITH THE INNER RACE MEMBER OF SAID TEST BEARING , DRIVING MEANS MOUNTED ON SAID HOUSING AND ADAPTED TO APPLY TORQUE TO THE OUTER RACE MEMBER OF SAID TEST BEARING, WHEREBY A TRANSMITTED TORQUE IS APPLIED TO THE SAID INNER RACE MEMBER AND SHAFT FROM THE SAID OUTER RACE MEMBER THROUGH THE SAID ROLLING ELEMENTS THEREBETWEEN AN ELECTRICAL SERVOLOOP ROTATION-RESTRAINING SYSTEM COMPRISING A SIGNAL GENERATOR AND A TORQUE GENERATOR EACH HAVING A ROTOR AND A STATOR RESPECTIVELY, THE SAID ROTORS BEING MOUNTED ON SAID SHAFT IN COAXIAL SYMMETRY THEREWITH, EACH OF THE SAID STATORS BEING MOUNTED ON SAID HOUSING IN OPERATIVE RELATIONSHIP WITH THE ROTOR ASSOCIATED THEREWITH, SAID SIGNAL GENERATOR BEING ADAPTED TO PRODUCE AN OUTPUT SIGNAL IN PROPORTION TO ANGULAR DISPLACEMENT OF ITS SAID ROTOR, ELECTRICAL CONNECTING MEANS FOR APPLYING SAID OUTPUT SIGNAL FROM SAID SIGNAL GENERATOR TO THE SAID TORQUE GENERATOR, SAID TORQUE GENERATOR BEING ADAPTED TO 